In general, a ball mill is configured as a cylindrical device, and is utilized for grinding crushed materials. Ball mills are widely used in production lines for powders such as cement, silicates, refractory material, fertilizer, glass ceramics, and the like. Ball mills are also used for ore dressing of both ferrous and non-ferrous metals. A ball mill is capable of grinding various ores and other materials either wet or dry. There are many types of grinding media suitable for use in a ball mill, each material having its own specific properties and advantages. Key properties of grinding media are size, density, hardness, and composition.
Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Different materials are used as media, including ceramic balls, flint pebbles and steel balls. An internal cascading effect reduces the material to a fine powder. Industrial ball mills can operate continuously, fed at one end and discharged at the other end. Large to medium-sized ball mills are mechanically rotated on their axis, but small ones normally consist of a cylindrical capped container that sits on two drive shafts (pulleys and belts are used to transmit rotary motion). High-quality ball mills are potentially expensive and can grind mixture particles to as small as 5 nm, enormously increasing surface area and reaction rates.
During the ball milling operation, the grinding media, e.g. the steel balls, wear down and need to be replenished. This has typically been a manual operation, which is both tedious and dangerous. Grinding balls need to be added often in order to maintain optimum grinding characteristics. Steel balls, for example, may need to be replenished at a rate of about 100 barrels per month. Each barrel weighs approximately 2,000 pounds, and the balls must be added to the system in a controlled fashion. This is generally a two-person operation. The task is further complicated by the fact that natural weathering causes bridging and agglomeration of the balls, which further heightens the danger and difficulty of controlled stepwise addition of the grinding media to the system.
The present inventors have developed an assembly for automatically feeding grinding media to a ball mill assembly which mitigates the danger and provides an assembly of elements for receipt of grinding media and controlled addition to one or more ball mill grinders, so as to insure that optimal grinding parameters are maintained.